1. Field of the Invention
The present invention relates to the field of high-purity filtration, especially high-temperature filtration in chemical, pharmaceutical and semiconductor industries where high reliability, easy maintenance, like a cartridge change, and performance like extremely low particle count are of prime importance.
2. Description of the Prior Art
Presently available filter housing assemblies use cartridges inserted into a cylindrical housing with a twist-top for tightening an O-ring against the housing in order to generate a sealed cavity for the cartridge, with an inlet and an outlet for the liquid to be filtered. The commercial filter cartridge is closed off at the top and the liquid enters the filter material under pressure to flow radially to a central tube-like space, then axially towards the exit duct at the bottom and the outlet. Usually the cartridge is held only by its two O-rings at its nose end in the bottom recess of the housing without a concentric hold at its top, possibly leading to a tilt and to leaks around the O-rings which in turn leads to uneven filtration and shortened cartridge lifetime. Together with the used cartridge filter housings are often thrown away amounting to economical and environmental waste. Often little attention had been paid to an easy installation of the filter housing and an economical replacement of filter cartridges for minimal process interruption.
It is an objective of the present invention to provide a filter housing for one cartridge with centering on its top to prevent tilting of the cartridge, thus preventing unreliable filtering. The housing can be made out of plastic materials like TEFLON(copyright) PVDF or of Polupropylen for liquid temperatures of about 190 centigrades (375 degrees F.) or of about 90 centigrades (194 degrees F.), respectively at pressures as high as 5 bars (70 psi). The housing assembly comprises a bottom and a top housing and a nut ring for fastening the housings together with an O-ring to form a sealed cavity for the cartridge, except for the inlet and the outlet. This O-ring between the housings and two O-rings around the nose of the cartridge, which seal against the pressure drop across the cartridge, are the only seals required. The air pocket in the cavity of the top housing provides a cushion against liquid level variations and thus pressure variations caused by pump action. The top housing is penetrated by a fixed vertical vent channel for stabilizing the liquid level if it drops below the lower vent channel opening. The bottom of the bottom housing carry cutouts to allow easy fastening on a wet bench with protruding bolts. Inlet and outlet are coaxial to facilitate plumbing connections. A filter cartridge change can easily be accomplished by unscrewing the nut ring, removing the top housing, pulling out the cartridge, inserting another cartridge, putting on the top housing and tightening the O-ring between the top and the bottom housing by tightening the nut ring.
An advantage of the present invention is that the sealing interfaces are joined together by a sliding action, cradling the O-ring and avoiding twisting and abrasive action on it.
Another advantage of the present invention is an easy change of the filter cartridge involving only one O-ring to be tightened by screwing a nut ring around top housing onto bottom without twisting the O-ring.